a.in contrast to the highly selective ion channels that connect a cell to the external medium, gap junction channels are __, but can be __

i.channel closure is probably triggered primarily by __of __subunits

ii.closer can also be triggered by changes in __ across the junction or abnormally high __

nonselective

gated

phosphorylation

connexin

voltage

cytosolic Ca2+ concentrations

i.gap junctions are involved in stimulation of a __

cardiac or smooth muscle

Cardiac stimulation by gap junctions:
1. contraction of the mammalian heart is stimulated by an __ generated in a small region of specialized heart muscle called the __, which acts as the heart’s __

electrical impulse

sinoatrial node

pacemaker

Cardiac stimulation by gap junctions:
2. the impulse spreads rapidly as a current of ions flows through __ from one __ cel to its neighbors, causing the cells to contract in __

gap junctions

cardiac muscle

synchrony

Smooth muscle stimulation:
3. similarly, the flow of ions through __ that interconnect __ in the wall of the esophagus or intestine leads to the generation of coordinated __ that move down the length of the wall

gap junctions

smooth muscle cells

peristaltic waves

i.gap junctions can put many tissues cells into __

1.important since a lot of highly active regulatory substances like __are small enough to fit through __--> __ have potential to integrate the activities of individual cells of a tissue into a __

intimate cytoplasmic contact

cAMP

gap-junction x2

functional unit

i.gap junctions also allow cells to cooperate metabolically by sharing key __, such as ATP, sugar phosphates, amino acids, and many __, which are small enough to pass through these intercellular channels

metabolites

coenzymes

1.__ (Cx), the proteins of which gap junctions are constructed, are members of a __

a.nearly __different __with distinct tissue-specific distributions

connexins

multigene family

20

connexins

a.__composed of different __ exhibit marked differences in __, __, and __

i.in some cases, __in neighboring cells that are composed of different __ are able to doct and form functional channels, whereas in other cases, they are not

connexons

connexins

conductance

permeability

regulation

connexons

connexins

1.these compatibility differences may play important roles in either __ or __ __ __between different types of cells in an organ

promoting or preventing

communication

i.a new type of communication system discovered consisting of thin, highly elongated tubules capable of conducting __ (3) __from one cell to another over long distances and transmit infectious viral particles and prions between cells

1.to date, these __ have been studied primarily in cultured cells

cell-surface proteins, cytoplasmic vesicles, and calcium signals

tunneling nanotubes

a.Plasmodesmata

i.plants, due to cell wall, are connected by these, which are __

1.lined by __ and usually contain a __, the __, derived from the __of the two derived from the __ of the two cells

cytoplasmic channels that pass through the cell walls of adjacent cells

plasma membrane

dense central structure

desmotubule

smooth endoplasmic reticulum

smooth ER

i.like __, they serve as sites of __, as substances pass through the __surrounding the __

ii.allow much larger molecules to pass between cells, since they __

gap junctions

cell-to-cell communication

annulus

desmotubule

dilate

1.discovery: vruses encoded a __ that interacted with the wall of the __and increased the __of the pore

a.plant cells produce their own __that regulate the flow of proteins and RNAs from cell to cell